1. Field of the Invention
In general, the invention relates to drivers for lighting, and in particular, to drivers for light-emitting diode (LED) light fixtures.
2. Description of Related Art
Light fixtures that use light-emitting diodes (LEDs) have become particularly popular in both residential and commercial lighting applications for a variety of reasons, including their relatively high efficiency and adaptability to a variety of different applications. While LED light fixtures are available in various types and with various power requirements, a fair number of the LED light fixtures currently on the market operate at low voltage using direct current (DC) power. The definition of “low voltage” varies depending on the authority one consults, but it generally refers to voltages under about 50V.
Low voltage DC poses a problem for fixture designers and for the carpenters and electricians who install the fixtures: the commercial and residential power grid operates at a much higher voltage, typically 110-240 volts, and uses alternating current (AC) power. Some standard voltages, particularly for industrial applications, may be higher still. Thus, in order to function in a residential or commercial installation, an LED fixture, e.g., operating at 24 VDC, will require a transformer-rectifier to convert the higher-voltage AC power to 24 VDC. That transformer-rectifier is together referred to as a “power supply,” or a “driver.” Even LEDs designed to operate at higher-voltage DC, e.g., 120V, typically need at least drive circuits and a rectifier, and to drive LEDs that have additional features (e.g., multi-color capability, selectable color temperature, etc.), the driver may need additional capabilities to produce power and control signals for those features as well. Of course, a driver is one more thing that a builder or electrician must find space to place, often within a wall or in another location that is hidden and difficult to access.
As LEDs have become more common and accepted in residential and commercial applications, consumers have sought to do with LEDs the same things that they are able to do with traditional incandescent lighting. Dimming—the ability to lower the light output of a lamp—is one of those things. While LEDs are inherently dimmable, legacy dimmers, intended for incandescent lighting operating on high-voltage AC power, are often not compatible with LEDs.
There are a number of dimmers that are designed to work with LEDs. For example, Elemental LED, Inc. of Emeryville, Calif. sells a combined, integrated driver and dimmer switch under the brand name SWITCHEX®. The SWITCHEX® driver-dimmer switch is configured to fit within a standard electrical single gang box (i.e., a standard electrical junction box configured to hold a single light switch). While the SWITCHEX® driver-dimmer switch is innovative and its form factor gives it compatibility with standard household and commercial lighting circuits without having to place a separate driver, the SWITCHEX® does have some disadvantages.
For one, the SWITCHEX® driver-dimmer switch is limited in the amount of power it can handle. Because of applicable standards for Class 2 electrical appliances, the SWITCHEX® driver can provide only 60 W (at 12 V) or 100 W (at 24 V) of power, whereas traditional dimmers and other electrical elements for incandescent lighting may be rated for up to 600 W of power.
Additionally, this particular driver-dimmer switch is currently manufactured in a limited number of colors and with a limited number of switch types and other options, and the aesthetic features of a switch can matter a great deal. Simply put, most people want all of their switches and related hardware to have a similar appearance. However, the consumer market for electrical switches, dimmers, and other common elements is controlled by only a few companies, and some switches and switch styles are protected by various intellectual property rights. Thus, in some cases, even if making a driver-dimmer switch in a particular style to match other existing fixtures would be possible or practical, it would be impermissible.
Beyond aesthetics, dimmer switches can be expensive pieces of hardware, and in any given home or commercial setting, there may be quite a few of them. Thus, for reasons of cost, convenience, or aesthetic fit, many consumers might prefer to keep their existing, legacy dimmer switches, and many installers prefer to buy the simplest components that are compatible with the greatest number of products.